Reel

ABSTRACT

A reel in which the planarity of a reel plate after insert molding may be ensured. The reel plate is formed into a concave shape, and by insert molding, the reel plate is made substantially flat. When a reel plate is insert molded, the reel plate is deformed in the direction to protrude in the direction to the outside of the reel by shrinkage stress of resin after molding. Therefore, by concaving the reel plate in advance into a concave shape, even if the reel plate is protruded by the shrinkage stress of the resin after insert molding, the amount of protruding may be absorbed by the amount of concaving, and the shape of the reel plate may be made substantially flat. That is to say, the planarity of the reel plate may be obtained. By doing so, the meshing of the reel gear that surrounds the reel plate with the drive gear on the rotation shaft side of the drive device may be improved.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C 119 from Japanese Patent Application No. 2006-119601, the disclosure of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reel for winding recording tape, such as magnetic tape or the like, thereon.

2. Description of the Related Art

Conventionally known are, recording tape cartridges with a storage reel, on which is wound magnetic tape, accommodated in a case, as disclosed, for example, in Japanese Patent Application Laid-Open (JP-A) No. 2005-259245. The reel is provided with a hub, configuring an axial central portion of the reel, for winding magnetic tape on the external peripheral surface thereof, and a top flange and a bottom flange that extend outside from the hub in the radial direction from respective ends in the axial direction.

Conventionally known are recording tape cartridges in which recording tape such as magnetic tape for use as a data recording medium, such as for a computer, is wound on a single reel, and the reel is rotatably accommodated within a case made of synthetic resin. A leader member of a leader pin and leader tape, or leader block, is provided at the leading end (free end) of the recording tape, and a mechanism for pulling out is provided on a drive device side, which pulls the leader member out from an opening in the recording tape cartridge, and winds the recording tape that is attached to the leader member onto a take-up reel on the drive device side.

There is also an annular reel plate that is able to be magnetically attached to a rotation shaft on the drive device side provided on the surface of the hub, and the reel is rotated under drive power from the rotation shaft in a state in which the rotation shaft is magnetically attached to the reel plate. Due to this, it is necessary to have a high precision of planarity for the reel plate.

However, since the reel plate is integrated to the hub by insert molding, deformation of the reel plate body may be generated by the extrusion pressure of the resin during molding or the shrinkage stress or the like of the resin after molding, and it is sometimes difficult to ensure the planarity of the reel plate. Therefore, sometimes the meshing precision deteriorates of the gear on the drive device side with the gear on the reel side.

SUMMARY OF THE INVENTION

A reel that can ensure the planarity of the reel plate after insert molding is provided according to the present invention.

A first aspect of the invention is a reel including: a hub, for winding recording tape thereon, the hub being a bottomed cylindrical shape; a reel plate, being magnetically attachable to a rotation shaft on a drive device side, insert molded to the bottom surface of the hub when formed into a concave shape and; the reel plate surface being substantially flat after being insert molding.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:

FIG. 1A is an outline perspective diagram of a reel of a recording tape cartridge, as seen from above, and FIG. 1B is an outline perspective diagram of a recording tape cartridge, as seen from below;

FIG. 2 is an outline cross-sectional diagram of when a reel of a recording tape cartridge according to an embodiment of the present invention is in a rotation locked position;

FIG. 3 is an outline cross-sectional diagram of when a reel of a recording tape cartridge according to an embodiment of the present invention is in a rotation permitting position;

FIG. 4 is an outline exploded perspective diagram of a reel and brake member of a recording tape cartridge and a rotation shaft of a drive device, according to an embodiment of the present invention, as viewed from above;

FIG. 5 is an outline exploded perspective diagram of a reel and brake member of a recording tape cartridge, according to an embodiment of the present invention, as viewed from below;

FIG. 6A is an outline plan diagram showing a clutch member in a state of being assembled to a reel, and FIG. 6B is a outline cross-section showing the clutch member in the state of being assembled to the reel;

FIG. 7 is an outline cross-section showing a reel plate of a reel according to an embodiment of the present invention;

FIG. 8 is an outline cross-section showing a mold for forming a hub of a reel according to an embodiment of the present invention;

FIG. 9 is an explanatory diagram showing a reel plate of a reel according to an embodiment of the present invention;

FIG. 10B is a graph showing a reel plate part on its own of a reel according to an embodiment of the present invention, and the deformation of the reel plate after forming, and FIG. 10A is a comparative example thereof;

FIG. 11 is an explanatory diagram showing the measurement direction of FIGS. 10.

DETAILED DESCRIPTION OF THE INVENTION

Herebelow, an exemplary embodiment of a drive device according to the present invention will be described in detail with reference to the drawings.

First, a recording tape cartridge (magnetic tape cartridge) 10 which can be loaded into a drive device will be described. Note that, for convenience of explanation, the direction of loading the recording tape cartridge 10 into the drive device of is denoted by arrow A, and this direction of arrow A is defined as the forward direction (front side) of the recording tape cartridge 10.

As shown in FIGS. 1A through 3, the recording tape cartridge 10 has a case 12. The case 12 is structured by an upper case 14 and a lower case 16 being joined together. Specifically, the upper case 14 is structured such that a substantially frame-shaped peripheral wall 14B extends down along the outer edge of a ceiling plate 14A that is substantially rectangular in plan view. The lower case 16 is structured such that a peripheral wall 16B stands up along the outer edge of a floor plate 16A which has a configuration substantially corresponding to that of the ceiling plate 14A. The case 12 is formed in a substantial box shape by the upper case 14 and the lower case 16 being joined together by ultrasonic welding or screws or the like in a state in which an open end of the peripheral wall 14B and an open end of the peripheral wall 16B abut one another.

At a corner portion of the case 12 at the leading side in the direction of loading the recording tape cartridge 10 into a drive device, the ceiling plate 14A, the peripheral wall 14B, the floor plate 16A and the peripheral wall 16B are respectively cut away, such that an opening 18, which is inclined with respect to the loading direction, is formed. A gear opening 20, which is circular and passes through the floor plate 16A, is formed in a substantially central portion of the floor plate 16A. The gear opening 20 is for exposing a reel gear 42, which will be described later. An annular rib 22 projects toward the inner side of the case 12 at the floor plate 16A at the edge of the gear opening 20, and is for positioning and for dustproofing a reel 28, which will be described later.

A pair of positioning holes 24, 26 is formed in a vicinity of the front end of the outer surface of the floor plate 16A of the case 12. The positioning holes 24, 26 of the pair are each formed in the shape of envelopes within projections (not illustrated) which stand erect from the floor plate 16A toward the interior of the case 12. The positioning holes 24, 26 are disposed so as to be separated from one another and located on an imaginary line which is orthogonal to the loading direction. The positioning hole 24, which is the positioning hole which is closer to the opening 18, is formed in a substantially square shape, as seen in bottom view, which circumscribes a positioning pin of a drive device. The positioning pin 26 is a long hole whose longitudinal direction runs along the aforementioned imaginary line, and whose width corresponds to the diameter of a positioning pin. Accordingly, when the recording tape cartridge 10 is loaded into a drive device and positioning pins are inserted into the respective positioning holes 24, 26, the recording tape cartridge 10 is correctly positioned in the horizontal directions (the left/right direction and the front/back direction) within the drive device.

Positioning surfaces 24A, 26A, which are finished so as to be smoother than the other portions of the floor plate 16A (the design surface of the floor plate 16A), are formed around the positioning holes 24, 26. When the positioning pins are inserted into the positioning holes 24, 26, the positioning surfaces 24A, 26A abut positioning surfaces of the drive device which are provided around the positioning pins. In this way, the vertical direction positioning of the recording tape cartridge 10 within the drive device is carried out.

As shown in FIG. 2, the single reel 28, which will be described later, is rotatably accommodated within the above-described case 12. A magnetic tape T serving as a recording tape is wound on the reel 28. A leader block 30, which serves as a pull-out member, is attached to the distal end of the magnetic tape T. When the recording tape cartridge 10 is not being used, the leader block 30 is accommodated and held at the inner side of the opening 18 of the case 12. In this state, the leader block 30 closes the opening 18, and impedes entry of dust and the like into the case 12.

An engaging recess 30A is formed at the distal end of the leader block 30. When the magnetic tape T is to be pulled-out within the drive device, a pull-out mechanism of the drive device engages the engaging recess 30A, and pulls the leader block 30 out of the case 12 and guides the leader block 30 to a take-up reel (not illustrated) of the drive device. Moreover, the end surface of the leader block 30 at the side opposite the engaging recess 30A is an arc-shaped surface 30B. The arc-shaped surface 30B is fitted to the take-up reel and forms a portion of the take-up surface around which the magnetic tape T is taken-up.

Next, explanation of the reel 28 will be given.

As shown in FIGS. 4 and 5, the reel 28 has a reel hub 32 which structures the axially central portion of the reel 28. The reel hub 32 is formed substantially in the shape of a hollow cylinder having a bottom, and has a cylindrical portion 34, around whose outer peripheral surface the magnetic tape T is wound, and a floor portion 36, which closes the bottom portion of the cylindrical portion 34. Moreover, a lower flange 38 extends coaxially and integrally at the radial direction outer side of a vicinity of the floor portion 36 side end portion (i.e., the bottom end portion) of the reel hub 32.

An upper flange 40 is fixed by ultrasonically welded coaxially to the reel hub 32 at a top end portion of the cylindrical portion 34, the upper flange 40 being an annular shape with an external diameter that is the same as that of the lower flange 38. That is to say, the reel 28 is such that, in the space between the pair of facing flanges of the lower flange 38 and the upper flange 40, magnetic tape T can be wound on the external peripheral surface of the cylindrical portion 34 of the reel hub 32.

A reel gear 42 is formed in an annular shape coaxial with the reel 28 in the vicinity of the cylindrical portion 34 on the bottom surface (outer surface) of the floor portion 36 of the reel hub 32. The reel gear 42 can mesh with a driving gear 108, which is provided at the distal end of a rotating shaft 100 of a drive device.

As shown in FIG. 4 and FIG. 5, an engaging gear 44 which is formed in an annular shape which is coaxial with the reel 28, is provided at the vicinity of the cylindrical portion 34 at the top surface (the inner surface) of the floor portion 36 of the reel hub 32. The engaging gear 44 is formed on an annular pedestal portion 46 which protrudes slightly from the inner surface of the floor portion 36, and can mesh with a braking gear 66 of a braking member 60, which will be described later.

Also, there are plural standing ribs 48 formed at even intervals in the circumferential direction at the outside in the radial direction of the engaging gear 44 (pedestal portion 46), each extending along the reel 28 axial direction and connecting the cylindrical portion 34 and the top surface of the floor portion 36.

A through hole 50 is provided at an axially central portion of the floor portion 36 of the reel hub 32. A boss portion 52 for a clutch stands erect along the edge of the through hole 50 from the top surface of the floor portion 36. The boss portion 52 for a clutch will be described later together with a clutch member 84.

The portions of the above-described reel 28, other than the upper flange 40, are formed integrally of a resin. Moreover, a reel plate 54, which is an annular plate formed of a magnetic material, is provided coaxially and integrally by insert molding at the inner side of the reel gear 42 at the bottom surface (outer surface) of the floor portion 36 of the reel hub 32.

Here, the reel plate 54 is formed using SPCC (JIS G3414 cold rolled steel plate and steel strip; longitudinal elastic modulus 205, 940 to 225, 550 (N/mm²) material, as shown in FIG. 7, with a thickness t of 1.0 mm and an external diameter dimension D of φ30 mm. A through hole 54A is formed at the central portion of the reel plate 54 to provide the reel plate 54 with an internal diameter dimension d of φ8 to 10 mm.

Through holes 54B are formed on the circumference of the same circle at a spacing of 120°. The through holes 54B are formed in a two step structure, with the top face side being narrower. It is possible for resin to flow inside the through holes 54B when molding, and the reel plate 54 is retained in the state in which the resin has flowed into the through holes 54B.

The reel plate 54 is formed into a concave shape (a saucer shape) by a press or the like such that in the height direction the dimension H of the external edge portion to the internal edge portion of the reel plate 54 is about 10 to 30 μm. The reel plate 54 may be flattened (the dotted lines in FIG. 7) by elastic deformation.

When the reel is molded, as shown in FIG. 8, (here, so that the relationship to the reel 28 is clear, the mold 120 for molding the reel 28 is shown in the closed state) the through hole 54A side floats away from the side of the mold, and the reel plate 54 is inserted in the mold 120, and the reel plate 54 is integrated with the reel hub 32.

The reel 28 is accommodated within the case 12, and is set on the annular rib 22 when the recording tape cartridge 10 is not in use. Specifically, the portion of the floor portion 36 at the outer side of the taper portion 43 (i.e., a vicinity of the inner edge of the lower flange 38) abuts the top end surface of the annular rib 22, and radial direction movement of the reel 28 is restricted due to the inner edge portion of the top end of the annular rib 22 being a taper surface 22A corresponding to the taper portion 43. Entry of dust or the like therefrom can thereby be impeded.

In this state, the reel 28 is positioned as a whole within the case 12, and the reel gear 42 and the reel plate 54 are exposed from the gear opening 20 (see FIG. 1B). Namely, the reel gear 42 faces the exterior of the case 12 from the gear opening 20, without projecting out from the outer surface (the bottom surface) of the floor plate 16A. Further, the through hole 50 faces the gear opening 20 through the through hole 54A of the reel plate 54.

In this way, the reel 28 can be operated, i.e., chucked (held) and driven to rotate, from the exterior of the case 12. Further, in this state, an annular restricting rib 56, which extends down from the ceiling plate 14A, is disposed within the top portion of the cylindrical portion 34 of the reel 28 (see FIG. 2). The outer peripheral surface of the restricting rib 56 is adjacent to the inner peripheral surface of the upper flange 40, and restricts horizontal movement of the reel 28 within the case 12.

As seen in FIG. 4, recording tape cartridge 10 has a braking mechanism 60 for impeding rotation of the reel 28 when the recording tape cartridge 10 is not in use. The braking member 60 has a base portion 62. The base portion 62 is substantially formed as a hollow cylinder which has a bottom and which opens downward, with a tubular portion 62A formed in the shape of a short tube, and a disc portion 62B which closes the top end of the tubular portion 62A. The outer diameter of the tubular portion 62A is smaller than the inner diameter of the engaging gear 44 (the pedestal portion 46). The inner diameter of the tubular portion 62A is larger than the outer diameter of the boss portion 52 for a clutch.

A ring portion 64 formed in an annular form extends outwardly in the radial direction along the entire periphery, from an axial direction intermediate portion at the outer peripheral portion of the base portion 62 (the tubular portion 62A). The braking gear 66 is provided along the entire periphery at the bottom surface of the ring portion 64. Namely, the braking gear 66 is formed in an annular form overall. The braking gear 66 is structured so as to be able to mesh with the engaging gear 44 of the reel 28.

The inner end portions of the respective teeth forming the braking gear 66 are connected by the tubular portion 62A. The outer end portions of the teeth, which are in a free state, are positioned slightly further inward, in the radial direction, than the outer edge of the ring portion 64. In other words, the ring portion 64 juts out further outwardly in the radial direction than the braking gear 66. More specifically, the outer diameter of the ring portion 64 is slightly larger than the outer diameter of the engaging gear 44, and the outer diameter of the braking gear 66 is slightly smaller than the outer diameter of the engaging gear 44. Moreover, an annular reinforcing rib 68 stands erect at the top surface of the ring portion 64 along the outer edge portion thereof, such that the rigidity of the ring portion 64 (the braking gear 66) is ensured.

As shown in FIG. 5, a slide-contact projection 70 projects from an axially central portion of the bottom surface of the disc portion 62B of the base portion 62 (i.e., the tubular portion 62A inner side). The distal end portion of the slide-contact projection 70 is formed in the shape of a substantially spherical surface, and substantially point-contacts the clutch member 84 which will be described later. The distal end of the slide-contact projection 70 is positioned slightly higher than the bottom end surface of the tubular portion 62A (i.e., at the inner side of the tubular portion 62A). On the other hand, a cross-shaped projection 72 stands erect at the top surface of the disc portion 62B. An insertion groove 72A, which is substantially cross-shaped in plan view, is formed in the cross-shaped projection 72. Through holes 74, which pass through the disc portion 62B in the direction of plate thickness thereof, are formed in the disc portion 62B.

The through holes 74 are formed, divided into four so as to communicate with the radial direction outer side portions of the insertion groove 72A, apart from at the axially central portion of the insertion groove 72A, which is formed in a cross-shape in plan view (i.e., except for the intersection portion of the insertion groove 72A). The through holes 74 are respectively formed in rectangular shapes. In this way, the respective through holes 74 are positioned adjacent to the radial direction outer side of the slide-contact projection 70, and open to the interior of the tubular portion 62A. Further, an annular rib 76 stands erect at the outer peripheral portion of the top end of the base portion 62. The top surface of the disc portion 62B between the rib 76 and the cross-shaped projection 72 is a spring receiving surface 78, which one end portion of a compression coil spring 82 (which will be described later) abuts.

The braking member 60, which has been described above, is inserted substantially coaxially in the cylindrical portion 34 of the reel hub 32 so as to be movable in the vertical direction (the axial direction of the reel 28). Namely, due to the braking member 60 moving in the vertical direction, the braking member 60 can be set at a position at which the braking gear 66 meshes with the engaging gear 44 of the reel hub 32 (a rotation locked position), and a position at which this meshing is released (a rotation permitted position).

A cross-shaped rib 80, which projects downward from the ceiling plate 14A of the case 12, is disposed in the insertion groove 72A of the cross-shaped projection 72 of the braking member 60. The cross-shaped rib 80 is formed in the shape of a detent which is formed as if two thin plates intersect one another orthogonally. Due to the cross-shaped rib 80 engaging with the cross-shaped projection 72 (the groove walls of the insertion groove 72A), rotation of the braking member 60 with respect to the case 12 is impeded. Accordingly, the braking member 60 impedes rotation of the reel 28 in a state in which the braking gear 66 meshes with the engaging gear 44 of the reel hub 32.

Note that the state in which the cross-shaped rib 80 is inserted in the insertion groove 72A is maintained over the entire stroke of movement of the braking member 60 in the vertical direction, such that the cross-shaped rib 80 also functions to guide the direction of movement of the braking member 60 in the vertical direction. Moreover, projecting pieces 80A extend from the bottom end portion of the cross-shaped rib 80 at positions corresponding to the respective through holes 74 of the braking member 60. The widths of the respective projecting pieces 80A (i.e., the lengths of the projecting pieces 80A in the radial direction of the braking member 60) are narrow than the lengths of the cross-shaped ribs 80, and correspond to the lengthwise dimensions of the respective through holes 74, and the projecting pieces 80A enter into respectively different ones of the through holes 74.

When the braking member 60 is positioned at the rotation locked position, the respective projecting pieces 80A are positioned within the insertion groove 72A. When the braking member 60 is at the released position (i.e., rotation permitted position), the projecting pieces 80A enter into the through holes 74 and project from the bottom surface of the disc portion 62B (i.e., pass through the through holes 74). In this way, due to the projecting pieces 80A being formed so as to extend, the cross-shaped rib 80 not only impedes rotation of the braking member 60 with respect to the case 12, but also, the amount thereof which is engaged with the braking member 60 (the depth of insertion thereof into the braking member 60) is greatly increased, and the cross-shaped rib 80 suppresses tilting of the braking member 60 with respect to the case 12. Further, the cross-shaped rib 80 which has this structure has an improved ability to guide the braking member 60 in the vertical direction. Note that, in the present embodiment, the engaged amount, in the axial direction, of the cross-shaped rib 80 (including the projecting pieces 80A) with the braking member 60 which is positioned at the rotation locked position, is set to be sufficiently larger than the entire stroke of movement of the braking member 60.

It is configured such that when the braking member 60 is positioned at the rotation locked position, radial direction movement of the reel 28 is restricted by the standing ribs 48, and that when the braking member 60 is positioned at the rotation permitted position, there is no fear of interference between the braking member 60 and the standing ribs 48 which are rotating together with the reel 28. Therefore, the standing ribs 48 are formed such that they are positioned adjacent to the reinforcing rib 68 of the ring portion 64 of the braking member 60 when positioned at the rotation locked position, and the top portions of the standing ribs 48 are cut away such that the gap between the standing ribs 48 and the reinforcing rib 68 of the braking member 60 positioned at the rotation permitted position is greater than or equal to a predetermined value. In this way, not only is movement of the reel 28 directly restricted by the case 12, but also, in a vicinity of the position of the center of gravity thereof, radial direction movement of the reel 28 with respect to the case 12 is restricted via the braking member 60. The recording tape cartridge 10 can also be loaded stably in upright-type drive devices (in which the axis of the reel 28 is the horizontal direction).

A compression coil spring 82 is disposed between the ceiling plate 14A and the spring receiving surface 78 of the braking member 60. One end portion of the compression coil spring 82 abuts the spring receiving surface 78, whereas the other end portion thereof abuts the ceiling plate 14A. This other end portion is positioned at the inner side of an annular wall portion 83 which projects at the outer side of the cross-shaped rib 80 at the ceiling plate 14A, such that the position of the compression coil spring 82 does not become offset in the radial direction.

Due to the urging force of the compression coil spring 82, the braking member 60 is urged downward, and usually, the braking gear 66 meshes with the engaging gear 44 such that inadvertent rotation of the reel 28 is reliably prevented (i.e., the braking member 60 is positioned at the rotation locked position). Further, due to this urging force, the reel 28, which meshes with the braking member 60 at the engaging gear 44, also is urged downward and abuts the annular rib 22 such that the reel 28 does not joggle within the case 12.

The recording tape cartridge 10 is provided with the clutch member 84 which is operated from the exterior at the time of releasing the state in which the reel 28 is locked by the braking member 60. The clutch member 84 is disposed between the floor portion 36 of the reel 28 and the braking member 60. The clutch member 84 has a clutch main body 86 which is formed as a substantially cylinder-shape. The outer diameter of the clutch main body 86 is formed so as to be slightly smaller than the through hole 54A of the reel plate 54, i.e., the slightly smaller than the diameter of the through hole 50 which coincides with the inner diameter of the boss portion 52 for a clutch.

As shown in FIG. 6B as well, the flat top end surface of the axially central portion of the clutch main body 86 is a slide-contact surface 86A which always abuts the slide-contact projection 70 of the braking member 60. The flat bottom end surface of the clutch main body 86, which is around a hollowed portion 86B that opens downward, is a press operation surface 86C. When the press operation surface 86C of the clutch member 84 is pressed, the clutch member 84 moves upward against the urging force of the compression coil spring 82, and moves the braking member 60 to the rotation permitted position.

The clutch member 84 has rotation restricting ribs 88 which jut out further toward the outer side in the radial direction than the outer peripheral surface of the clutch main body 86. Plural of the rotation restricting ribs 88 (three in the present embodiment) are provided at uniform intervals in the peripheral direction of the clutch main body 86. The rotation restricting ribs 88 are disposed in a radial arrangement as seen in plan view. The respective rotation restricting ribs 88 project further upward than the slide-contact surface 86A, so as to extend between (connect) the top end surface of the clutch main body 86 around the slide-contact surface 86A and the outer peripheral surface of the clutch main body 86 in a vicinity of the top end surface thereof.

The rotation restricting ribs 88 are disposed within rotation restricting grooves 90 which are formed in a recessed manner from the inner edge portion of the boss portion 52 for a clutch. Namely, three of the rotation restricting grooves 90 are provided at uniform intervals in the peripheral direction of the boss portion 52 for a clutch. The rotation restricting grooves 90 open upwardly at the top end of the boss portion 52 for a clutch. In this way, the clutch member 84 can move in the vertical direction while being guided, at the rotation restricting ribs 88, by the rotation restricting grooves 90 of the boss portion 52 for a clutch.

Also when the clutch member 84 moves upward and the braking member 60 is positioned at the rotation permitted position, the state in which each of the rotation restricting ribs 88 are disposed in the respective rotation restricting grooves 90 of the boss portion 52 for a clutch is maintained. In this way, the clutch portion 84 cannot rotate relative to the reel 28, i.e., always rotates integrally with the reel 28.

In addition, because the rotation restricting grooves 90 are closed at the bottom end portion of the boss portion 52 for a clutch, falling-out of the clutch member 84 from the reel hub 32 can be impeded by the rotation restricting ribs 88 and the rotation restricting grooves 90. Further, in the present embodiment, separately from the rotation restricting ribs 88, the clutch member 84 has seat ribs 92 which impede falling-out of the clutch member 84 from the reel hub 32.

Plural of the seat ribs 92 are provided at uniform intervals in the peripheral direction of the clutch main body 86. In the present embodiment, a total of three of the seat ribs 92 are provided at intermediate portions, in the peripheral direction, between the respective rotation restricting ribs 88. In the same way as the rotation restricting ribs 88, the seat ribs 92 project upward and outward in the radial direction so as to extend between the top end surface of the clutch main body 86 around the slide-contact surface 86A and the outer peripheral surface of the clutch main body 86 in a vicinity of the top end surface thereof, and are disposed in a radial arrangement as seen in plan view.

The respective seat ribs 92 are disposed in stopper grooves 94 which are recessed in from the inner edge portion of the boss portion 52 for a clutch. Namely, each of the stopper grooves 94 are provided at uniform intervals in the peripheral direction of the boss portion 52 for a clutch, at the respective intermediate portions in the peripheral direction between the respective rotation restricting grooves 90. The stopper grooves 94 are open upwardly at the top end of the boss portion 52 for a clutch. The top surfaces of the floor portions which close the bottom end portions of the stopper grooves 94 are stopper surfaces 94A. When the braking member 60 is at the rotation locked position, the bottom end surfaces of the seat ribs 92 abut (sit on) the stopper surfaces 94A.

The clutch main body 86, the rotation restricting ribs 88, and the seat ribs 92 of the clutch member 84 are formed integrally by resin molding. As shown in FIG. 6B, the heights of the top end surfaces of the respective rotation restricting ribs 88 and the respective seat ribs 92 coincide. However, the bottom end surfaces of the rotation restricting ribs 88 are formed to be positioned lower than the bottom end surfaces of the seat ribs 92. In correspondence therewith, the top ends of the stopper grooves 94 and the rotation restricting grooves 90, which both are open at the top end of the boss portion 52 for a clutch, coincide, but the floor surfaces of the rotation restricting grooves 90 are positioned lower than those of the stopper surfaces 94A of the stopper grooves 94. In other words, the rotation restricting ribs 88 are longer, in the vertical direction, than the seat ribs 92, and the rotation restricting grooves 90 are deeper, in the vertical direction, than the stopper grooves 94.

By making the amount by which the rotation restricting ribs 88 and the boss portion 52 for a clutch can be engaged (i.e., the amount by which the rotation restricting ribs 88 can be inserted into the rotation restricting grooves 90) large, the stress received from the reel 28 when the reel 28 rotates can be mitigated, and also, the ability to guide the clutch member 84 when the clutch member 84 is moving up and down improves, and joggling of the clutch member 84 also when the braking member 60 is positioned at the rotation permitted position is suppressed.

As shown in FIG. 6A, in order to further suppress such joggling, a clearance C1 at one peripheral direction side between the rotation restricting rib 88 and the rotation restricting groove 90 is made as small as possible while ensuring that the sliding resistance at the time when the clutch member 84 moves up and down is not excessive. Moreover, the thickness of the rotation restricting rib 88 (i.e., the thickness thereof in the peripheral direction of the clutch member 84) is made to be as thin as possible within a range which does not present problems with respect to strength. The dimensional accuracy, resulting from the resin molding, of the rotation restricting rib 88 is high. Therefore, the clearance C1 can be made to be even smaller.

On the other hand, the thickness of the seat rib 92 (i.e., the thickness thereof in the peripheral direction of the clutch member 84) is sufficiently larger than the thickness of the rotation restricting rib 88. In this way, when the seat ribs 92 abut the stopper surfaces 94A, sufficient rigidity can be ensured with respect to the urging force of the compression coil spring 82, which is applied via the braking member 60. By making the seat ribs 92 thick, the resin flowability at the time of molding is relatively poor. However, due to the seat ribs 92 being shorter than the rotation restricting ribs 88 as described above, effects stemming from poor flowability are hardly felt.

In addition, the seat ribs 92, which are formed to be thick and whose dimensional accuracy is inferior to that of the rotation restricting ribs 88, are formed such that there is no need for them to function to suppress joggling of the clutch member 84. A clearance C2, in the peripheral direction and between the seat rib 92 and the stopper groove 94, is formed to be greater than the clearance C1. In this way, sliding resistance when the clutch member 84 moves up and down, either is not generated, or is markedly suppressed.

The heights (i.e., the positions of the top ends) of the rotation restricting ribs 88 and the seat ribs 92 are determined (see FIG. 3) such that the rotation restricting ribs 88 and the seat ribs 92 do not interfere with the projecting pieces 80A of the case 12, which pass through the disc portion 62B of the braking member 60, at the time when the clutch member 84 moves upward and the braking member 60 is positioned at the rotation permitted position.

At the above-described clutch member 84, in the state in which the rotation restricting ribs 88 are inserted in respectively different rotation restricting grooves 90 and the seat ribs 92 are inserted in respectively different stopper grooves 94, the clutch main body 86 is inserted through the through hole 50 and the through hole 54A. Further, usually, the respective seat ribs 92 are maintained in a state of abutting the stopper surfaces 94A, by the urging force of the compression coil spring 82 which is applied via the braking member 60.

In this state, the bottom end surfaces of the rotation restricting ribs 88 are separated slightly from the floor surfaces of the rotation restricting grooves 90 (see FIG. 6B), and the vertical direction position of the press operation surface 86C is positioned slightly (in the present embodiment, 0.1 mm) above the tips of the teeth of the reel gear 42. As the reel gear 42 meshes with the driving gear 108 of the drive device, the clutch member 84 is pressed by a release portion 114 of the drive device and moves upward.

Next, operation of the present embodiment will be described.

When the recording tape cartridge 10 having the above-described structure is not being used as shown in FIG. 2, due to the urging force of the compression coil spring 82, the braking member 60 is positioned at the rotation locked position, and the braking gear 66 is meshing with the engaging gear 44. Therefore, rotation of the reel 28 with respect to the case 12 is impeded. At this time, the reel gear 42 of the reel 28 is exposed from the gear opening 20, and the clutch main body 86 of the clutch member 84 is inserted through the through hole 50 and the through hole 54A and faces the gear opening 20.

On the other hand, when the magnetic tape T is to be used, the recording tape cartridge 10 is loaded into a bucket (not illustrated) of a drive device along the direction of arrow A as shown in FIG. 1A. When the recording tape cartridge 10 is loaded to a predetermined depth in the bucket, the bucket is lowered. The rotating shaft 100 of the drive device relatively approaches the gear opening 20 of the case 12 (i.e., moves upward), and holds the reel 28. Specifically, while the reel plate 54 is attracted and held by the magnet 110 in a non-contact state, the driving gear 108 of the rotating shaft 100 meshes with the reel gear 42.

Accompanying this meshing of the reel gear 42 and the driving gear 108, i.e., the relative movement of the rotating shaft 100 toward the side near the case 12 in the axial direction, the release portion 114 of the rotating shaft 100 abuts the press operation surface 86C of the clutch member 84, and presses the clutch member 84 upward against the urging force of the compression coil spring 82. In this way, the braking member 60, which is abutting the clutch member 84 at the slide-contact projection 70, also moves upward, and the meshing of the engaging gear 44 and the braking gear 66 of the braking member 60 is released.

That is, the brake member 60 is moved to the rotation permitting position relative to the reel 28. Then the release portion contacts the press operation surface 86C, and when the rotation shaft 100 is relatively moved upward, against the biasing force of the compression coil spring 82, the reel 28 is lifted upwards with the clutch member 84 and the brake member 60 (without any relative displacement therebetween), and the brake member 60 reaches the absolute rotation permitting position (relative to the case 12), and also the lower flange 38 is separated from the annular rib 22 (from the taper surface 22A). By doing so, the reel 28 is raised in the case 12, and enters a state in which it does not contact the internal surfaces of the case 12 and is able to rotate.

Due to the lowering of the bucket, i.e. the recording tape cartridge 10, within the drive device, the positioning pins of the drive device enter into the positioning holes 24, 26 of the case 12, and the positioning surfaces of the drive device abut the positioning surfaces 24A, 26A of the case 12. In this way, the recording tape cartridge 10 is positioned in the horizontal direction and the vertical direction with respect to the drive device.

The pull-out mechanism of the drive device pulls the leader block 30 out from the case 12 and guides the leader block 30 to the take-up reel of the drive device, while a pull-out pin (not illustrated) of the pull-out mechanism engages with the engaging recess 30A of the leader block 30. Then, the leader block 30 is fitted into the take-up reel, and the arc-shaped surface 30B forms a portion of the take-up surface on which the magnetic tape T is taken up.

When the leader block 30 rotates integrally with the take-up reel in this state, the magnetic tape T is pulled out from the case 12 through the opening 18 while being taken-up onto the reel hub of the take-up reel. At this time, the reel 28 of the recording tape cartridge 10 rotates synchronously with the take-up reel due to the torque of the rotating shaft 100 which is transmitted by the driving gear 108 which meshes with the reel gear 42.

Information is recorded onto the magnetic tape T or information recorded on the magnetic tape T is played back by a recording/playback head disposed along a predetermined tape path of the drive device. At this time, the slide-contact projection 70 of the braking member 60, which cannot rotate with respect to the case 12, slidingly contacts the slide-contact surface 86A of the clutch member 84 which rotates together with the reel 28 with respect to the case 12.

On the other hand, when the magnetic tape T is rewound onto the reel 28 and the leader block 30 is held in a vicinity of the opening 18 of the case 12, the drive device raises the bucket in which the magnetic tape cartridge 10 is loaded. After the bucket has been raised, the meshing of the reel gear 42 and the driving gear 108 is cancelled, the abutment of the release surface 114A and the slide-contact surface 86A of the clutch member 84 is released, and the clutch member 84 is moved downward, together with the braking member 60, by the urging force of the compression coil spring 82 (with the state of abutment between the clutch member 84 and the braking member 60 maintained).

In this way, the seat ribs 92 of the clutch member 84 abut the stopper surfaces 94A, and the braking gear 66 of the braking member 60 meshes with the engaging gear 44. Namely, the braking member 60 is returned to the rotation locked position at which the braking member 60 impedes rotation of the reel 28 with respect to the case 12. Moreover, as the braking member 60 and the clutch member 84 move due to the urging force of the compression coil spring 82, the reel 28 also moves downward. The reel gear 42 is returned to its initial state of being exposed from the gear opening 20, while the lower flange 38 of the reel 28 is made to abut the annular rib 22. In this state, the recording tape cartridge 10 is discharged from the bucket.

However, in the present invention, as shown in FIGS. 7 and 9, the reel plate 54 is formed in a concave shape (saucer shape), and it is configured such that after insert molding the shape of the reel plate 54 is flat (the difference in the height direction between the outer edge portion and the inner edge portion of the reel plate 54 is between 0 and 20 μm). When a reel is inset molding using a flat-shape reel plate then, as shown in FIG. 10A, the reel plate deforms in the direction to protrude out to the outside of the reel (to the top in the figure), due to the extrusion pressure of the resin when molding or due to the shrinkage stress of the resin after insert molding (FIG. 10A and FIG. 10B show the results when the profile of the top surface of the reel plate 54 is measured along the direction of the arrow in FIG. 11).

Therefore, as shown in FIG. 7, the reel plate 54 is made in advance into a saucer shape, made into a concave to the inside direction of the reel, the reel plate 54 is inset in the mold 120 such that the through hole 54A side of the reel plate 54 floats away from the mold 120. Then, by pouring resin into the mold 120, with the extrusion pressure when molding and the shrinkage stress of the resin and the like after insert molding, the reel plate 54 is protruded toward the outside direction of the reel, the concave amount (dimension H) is eliminated, and, as shown in FIG. 9, the profile of the reel plate 54 becomes substantially flat. Namely, the planarity of the reel plate 54 may be obtained, and, as a result, good meshing of the reel gear 42 surrounding the reel plate 54 and the drive gear 108 of the rotation shaft 100, is achieved.

Here, the reel plate 54 is formed into a saucer shape using SPCC material, with a thickness t of 1.0 mm and an external diameter dimension D of φ30 mm, the through hole 54A formed giving an internal diameter dimension d of φ8 to 10 mm, the reel plate 54 being formed in such a manner that in the height direction the dimension H between the outer edge portion and the inner edge portion of the reel plate 54 is about 10 to 30 μm.

The reel plate 54 may be elastically deformed to become flat (the dotted line) and if the stress that is making the reel plate 54 flat is released, the reel plate 54 will return to its original state of a concave shape (saucer shape). That is to say, if the insertion molded reel plate 54 is detached from the bottom portion 36 of the reel hub 32, then the reel plate 54 will return to its original state.

In the above the height direction dimension H from the outer edge portion to the inner edge portion of the reel plate 54 has been set to about 10 to 30 μm, however, it is sufficient that the reel plate 54 may be flattened within the range of elastic deformation of the reel plate 54, but the dimension H is set about 30 μm in this embodiment. However, this dimension H is different depending on the material, thickness and outline shape of the reel plate 54. Here, the present invention is also applicable to a type of reel plate that does not have a through hole 54A formed therein.

In the above, the material used for the reel plate 54 was SPCC, but there is no limitation to this material and it is sufficient as long as it is a magnetic material. For example, SUS 410 or the like may be used.

Note that, in the above-described embodiment, the recording tape cartridge 10 has the leader block 30. However, the present invention is not limited to the same. For example, the recording tape cartridge 10 may be structured such that a small, cylindrical leader pin is attached as a leader member to the distal end of the magnetic tape T, or may be structured so as to have a shielding member which opens and closes the opening 18 (a sliding door or the like which moves along a predetermined straight line or arc).

In addition, the magnetic tape T is used as the recording tape. However, the present invention is not limited to the same. It suffices for the recording tape to be interpreted as an information recording/playback medium which is shaped as an elongated tape and on which information can be recorded and from which recorded information can be played back. It goes without saying that the recording tape cartridge relating to the present invention can be applied to recording tapes of any recording/playback systems.

A first aspect of the invention is a reel including: a hub, for winding recording tape thereon, the hub being a bottomed cylindrical shape; a reel plate, being magnetically attachable to a rotation shaft on a drive device side, insert molded to the bottom surface of the hub when formed into a concave shape and; the reel plate surface being substantially flat after being insert molding.

According to the above aspect, by forming the reel plate concaved and insert molding in the mold with the central portion of the reel plate floated away from the side of the mold, the surface of the reel plate after insert molding is substantially level.

When the reel plate is being formed as an insert, the reel plate unfortunately tends to deform in the direction to protrude out towards the outside of the reel, due to the extrusion pressure of the resin during forming or the shrinkage stress of the resin after insert molding. Because of this, if the reel plate is made in advance into a concave shape, even if the reel plate protrudes at the time of insert molding due to the extrusion pressure of the resin or the shrinkage stress of the resin after insert molding, an amount of the protrusion of the concave amount may be absorbed. That is to say, planarity of the reel plate may be obtained. By doing so, good meshing of the gear surrounding the reel plate with the gear on the rotation shaft side may also be achieved.

In the above aspect, the amount of concave of the reel plate should be within such a range that the reel plate may be made planar within the elastic deformation range thereof.

According to the above aspect, in order to flatten the reel plate within the elastic deformation range of the reel plate, if the reel plate is removed from the bottom surface of the hub then the reel plate will return to its original state (concave shape).

A second aspect of the invention is a reel including: a hub, for winding recording tape thereon, the hub being a bottomed cylindrical shape; a reel plate; a flange, wherein the reel plate is initially formed into a concave shape when viewed in cross-section, but after the reel is molded the reel plate is substantially flat in cross-section.

A third aspect of the invention is a recording tape cartridge including a reel of the above aspects.

A fourth aspect of the invention is a reel manufacturing method for a reel including a bottomed cylindrical hub, a reel plate, and a flange, the method including: forming the reel plate into a concave shape; inserting the reel plate into a mold; and integrally forming the reel plate with the hub and the flange.

By each of the above configurations, the present invention is able to ensure the planarity of the reel plate.

The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The exemplary embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents. 

1. A reel comprising: a hub, for winding recording tape thereon, the hub being substantially a bottomed cylindrical shape; a reel plate, being magnetically attachable to a rotation shaft on a drive device side, being formed into a concave shape, and being insert molded to the bottom surface of the hub and; the reel plate surface being substantially flat after being insert molded.
 2. The reel according to claim 1, wherein an amount of concavity of the reel plate is such that the reel plate is configured to be flattened within the range of elastic deformation of the reel plate.
 3. The reel according to claim 1, wherein an amount of concavity of the reel plate is determined according to the material, thickness and/or outline shape of the reel plate.
 4. A reel comprising: a hub, for winding recording tape thereon, the hub being substantially a bottomed cylindrical shape; a reel plate; a flange, wherein the reel plate is initially formed into a concave shape when viewed in cross-section, and after the reel is molded the reel plate is substantially flat in cross-section.
 5. A recording tape cartridge comprising a reel according to claim 1 or claim
 4. 6. A reel manufacturing method for a reel comprising a bottomed cylindrical hub, a reel plate, and a flange, the method comprising: forming the reel plate into a concave shape; inserting the reel plate into a mold; and integrally forming the reel plate with the hub and the flange. 